Cooling and low temperature liquefaction of gaseous mixtures with multicomponent refrigerant

ABSTRACT

An apparatus for cooling and liquefying a gaseous mixture by means of a refrigerant fluid formed of a plurality of constituents, comprising a gas compressor, a plurality of tanks for separating gas from liquid and two series of counter current exchangers, said exchangers, for the cooling and liquefaction, being placed at increasing heights so as to provide for a circulation by gravity, along the various exchangers, of the refrigerant liquid injected at the head of each exchanger, and its mixture with the refrigerant gases, said refrigerant gases being liquefied by successive fractions at lower and lower temperatures in a first one of said two series of exchangers and used for cooling and liquefying the gaseous mixture in the other one of said series of exchangers, wherein in at least one series of exchangers at least the exchangers working at the two lowest temperatures are forming part of a unitary assembly in which the refrigerant fluid circulates downwardly, whereas in the other exchangers the refrigerant fluid circulates upwardly.

United States Patent [1 1 Ferret July 24, 1973 COOLING AND LOW TEMPERATURE LIQUEFACTION OF GASEOUS MIXTURES [73] Assignee: Compagnie Francaise DEtudes Et De Construction Technip, Rueil-Malmaison, France 1 221 Filed: Sept. 3, 1970 211 A l. No.: 69,327

[30] Foreign Application Priority Data OTHER PUBLICATIONS Kleemenko, A. P.; One Flow Cascade Cycle, Pergamon Press 1960 pages 34-39.

Primary Examiner-Norman Yudkoff Assistant Examiner-Arthur F. Purcell Att0rney-Flynn and Frishauf [57] ABSTRACT An apparatus for cooling and liquefying a gaseous mixture by means of a refrigerant fluid formed of a plurality of constituents, comprising a gas compressor, a plurality of tanks for separating gas from liquid and two series of counter current exchangers, said exchangers, for the cooling and liquefaction, being placed at increasing heights so as to provide for a circulation by gravity, along the various exchangers, of the refrigerant liquid injected at the head of each exchanger, and its mixture with the refrigerant gases, said refrigerant gases being liquefied by successive fractions at lower and lower temperatures in a first one of said two series of exchangers and used for cooling and liquefying the gaseous mixture in the other one of said series of exchangers, wherein in at least one series of exchangers at least the exchangers working at the two lowest temperatures are forming part of a unitary assembly in which the refrigerant fluid circulates downwardly, whereas in the other exchangers the refrigerant fluid circulates upwardly.

6 Claims, Drawing Figure COOLING AND LOW TEMPERATURE LIQUEFACTION OF GASEOUS MIXTURES WITH MULTICOMPONENT REFRIGERANT The present invention relates to an apparatus for the cooling and liquefaction of gaseous mixtures.

There has been described in US. Pat. No. 3,364,685 an apparatus for the cooling and liquefaction of gas eous mixtures, comprising a gas compressor, a plurality of tanks for separating gases and liquids, and two series of counter-flow exchangers, these cooling and liquefaction exchangers being located at increasing heights in order to permit the circulation by gravity along the various exchangers, of the refrigerant liquid injected at the head of each exchanger, and its mixture with the refrigerant gases.

The refrigerant fluid utilized is a mixture having a number of constituents which is liquefied by successive fractions in one of the series of exchangers at lower and lower temperatures, and is utilized for cooling and liquefying the gaseous mixture in an exchange column containing the other series of exchangers.

This apparatus permits an increase in the flow-rate of refrigerant gas through the exchange column intended for the cooling and liquefaction of the gaseous mixture, in the downward direction of this column, in consequence of the progressive boiling of the refrigerant liquid fractions. The result is that the diameter of the exchange column is larger at the base than at the top, which makes the construction more stable and more rigid, and also more compact. Furthermore, the upper zone of the column, which is the coldest, is the farthest away from the ground, which facilitates its thermal insulation. I

It has however been found that the circulation of the gas and of the refrigerant liquid during the course of boiling in the downward direction results in coefficients of exchange which are not so good as when the circulation is carried out in the upward direction.

In the case of an upward circulation, the flow of gas carries away droplets of liquid in a rising movement and causes a more intense stirring of these droplets with the gas.

This latter solution has however the disadvantage of requiring a flow-rate of gas sufficient to carry away the droplets of refrigerant liquid, without having the advantages of the downward circulation. Now, if the coldest liquid fractions of refrigerant fluid injected into the exchange column are strongly refrigerated, the quantity of gas formed atthe moment of their injection into the respective exchanger is too small to ensure this carrying away. This takes place especially in the case where a substantial refrigeration of the refrigerant fluid is necessary in order to obtain the. very low temperatures necessary for complete liquefaction of the gas to be liquefied.

In order toovercome this disadvantage, it has been proposed to establish a circulation of auxiliary gas which, in the coldest zone of the exchange column, namely the lower portion, ensures the desired carrying away action. This arrangement however results in a substantial complication of the apparatus described in the main patent and also of the general operation.

The present invention has for its object to resolve the problem set by the carrying away of droplets of refrigerent fluid in a simple and effective manner while at the same time ensuring satisfactory thermal insulation of the exchange zone at the lowest temperature.

According to the invention, the apparatus for cooling and liquefaction of gaseous mixtures by means of a refrigerant fluid having a number of constituents, comprising a gas compressor, a plurality of tanks for the separation of gas and liquid, and two series of counterflow exchangers, the refrigerant fluid being liquefied by successive fractions at lower and lower temperatures in one of the series of exchangers and utilized to cool and liquefy the gaseous mixture in the other series of exchangers, is characterized in that, for at least'one of the series of exchangers, the exchangers working at the two lowest temperatures at least are integrated in a unitary assembly in which the circulation of refrigerant fluid takes place from the top to the bottom, while in the other exchanger or exchangers, the circulation of the refrigerant fluid takes place in the opposite direction.

By virtue of this arrangement, the advantages resulting from the downward streaming action and the thermal insulation are retained in the zones working at the lowest temperatures, and the coefficient of exchange in the zones working at the higher temperatures is improved.

Other particular features of the invention will be brought out in the description which follows below, given by way of example and not in any limitative sense, reference being made to the accompanying drawing, in which:

The single FIGURE shows diagrammatically an apparatus for the liquefaction of gaseous mixtures.

The liquefaction apparatus shown comprises a compressor 1, in which a refrigerant fluid having a number of constituents is compressed and a condenser 2 in which the compressed fluid is partly condensed and is directed to a tank 3 in which the liquid and vapour phases are separated. The vapour is sent into an exchanger 4 while the condensate L1 is directed on the one hand towards the top of the exchanger 4 and on the other hand towards the central zone of a column 5 constituting a unitary exchange assembly. The liquid L1 is injected into this column in the upward direction by an injection head 6; a valve 7 enables the flow-rate of this liquid to be regulated at the inlet of the column 5, while a valve 8 regulates the flow of liquid directed towards the exchanger 4.

The gaseous mixture to be liquefied, which passes into the upper portion of the column 5, is cooled in a first exchange zone of this column comprising an exchanger tube 9 through which passes the gaseous mixture.

The refrigerant fluid partly condensed in the exchanger 4 is directed towards a tank 10 in which the liquid and vapour phases of this fluid are separated. The vapours issuing from the base of the exchanger 4 are sent to the compressor 1.

The liquid L2 contained in the tank 10 is directed on the one hand towards the top of an exchanger 11 in which the vapour coming from the tank 10 is partly condensed and on the other hand, towards the base of the column 5, into which it is injected in the upward direction by an injection head 12 in order to cool still further the gaseous mixture passing through an exchanger tube 13in a second exchange zone. Valves 14 and [5 permit the regulation of the flow of the liquid L2 at the inlet to the column 5 and to the exchanger 11 respectively. The vapours issuing-from of the base of the exchanger 11 are introduced into the top of the exchanger 4 at the same time as the liquid L1.

The refrigerant fluid partly condensed in the exchanger 11 is directed towards a tank 16 in which the liquid and vapour phases of this fluid are separated.

The liquid L3 contained in the tank 16 is directed, on the one hand towards the top of the exchanger 17 in which the vapour coming from the tank 16 is completely condensed, and on the other hand to the central zone of a column 18 constituting a further exchange unit. The liquid L3 is injected into this column in the downward direction by an injection head 19, the liquid L4 coming from the exchanger 17 being injected at the top of this column, also in the downward direction, by an injection head 20. The gaseous mixture to be liquefled which is sent from the column to the column 18 passes through the exchanger tubes 21, 22, forming in the column 18 the two exchange zones at the lowest temperatures.

The liquefied gaseous mixture issuing from the column 18 is directed towards storage tanks, its flow-rate being regulated by a valve 23. The refrigerant fluid in the gaseous state, circulating from the top to the bottom in the column 18, together with the residual refrigerant liquid is conveyed through conduit 24 to the base of the column 5. The flow of gas issuing from the column 18 is then sufficiently large to ensure, in the column 5 the carrying away effect in the upward direction of the droplets of regrigerant liquid which may either come from the column 18 or from the column 5.

Valves 25 and 26 permit the regulation of the flow of the refrigerant liquids L3 and L4 respectively at the inlet to the column 18 and a valve 27 regulates the flow-rate of liquid L3 at the inlet of the exchanger 17.

The vapours issuing from the base of the exchanger 17 are introduced at the same time as the liquid L2 into the top of the exchanger 11.

In addition to the advantages previously indicated, due to the separation of the two sets of exchangers 5 and 18, the arrangement described provides considerable simplification of the setting to work of the apparatus. In fact, in order to obtain in the conduit 24 a flow of gas in the neighbourhood of the minimum flow necessary for normal working, it is only necessary to inject first the liquids L4 and L3, the valves 7 and 14 being closed. As soon as this flow-rate is reached, the liquids L1 and L2 can be injected, the upward movement of the droplets of refrigerant liquid in the column 5 being thus ensured by the flow of gas. This obviates the necessity of utilizing secondary circulations of gas during the starting-up period.

It will of course be understood that the invention is not limited to the form of construction described, which has been given by way of illustrative example onl Thus, the same arrangement may be adopted for the exchangers serving for the liquefaction by successive fractions of the refrigerant fluid. ln addition,'the number of exchangers in the columns 5 and 18 may be variable; the column 5 may be dissociated to form individual separate exchangers in which the circulation of the refrigerant fluid is effected in the upward direction.

What I claim is:

1. Apparatus for cooling and liquefying a gaseous mixture by indirect contact thereof with a multicomponent refrigerant fluid, comprising in combination a gaseous compressor for compressing said refrigerant fluid,

a plurality of tanks in fluid communication with said compressor for separating gaseous and liquid phase of said multicomponent refrigerant fluid,

conduit means for connecting said tanks,

a first counter-current cryogenic exchanger unit A in which a first fraction of the refrigerant fluid is circulated, said first exchanger unit A including first means for passing said first fraction of the refrigerant fluid in an upward direction therein and second means for passing said gaseous mixture in a downward direction therein to produce a countercurrent exchange of said first fraction of the refrigerant fluid with said gaseous mixture and to refrigerate said gaseous mixture,

a second counter-current cryogenic exchanger unit B in which a second fraction of the refrigerant fluid is circulated, said second exchanger unit B including third means for passing said second fraction of the refrigerant fluid in a downward direction therein and fourth means for passing said refrigerated gaseous mixture from said first exchange unit A in an upward direction therein to produce a counter-current exchange of said second fraction of the refrigerated fluid with said refrigerated gaseous mixture; wherein said second fraction of the refrigerant fluid so circulated downwardly in exchanger B is at a lower temperature than said first fraction of the refrigerant fluid in said exchanger conduit means for connecting the refrigerated gaseous mixture between said exchangers A and B, and

conduit means for passing said gaseous mixture to and from said exchangers A and B.

2. Apparatus of claim 1, wherein said second exchanger unit B comprises two exchangers stages positioned one above the other.

3. Apparatus of claim 2, wherein said third means includes means for introducing a fraction of the refrigerant fluid at the lowest temperature at an upper portion of said second exchanger unit B for downward circulation therein, and for introducing another fraction of the refrigerant liquid at the next preceeding temperature stage at an upper portion of the lower of said two exchanger stages for downward circulation therein.

4. Apparatus of claim 1, wherein in each of said first and second exchanger units A and B, said gaseous mixture isconfined in an exchanger conduit and said exchanger units A and B include means for passing the refrigerant fluid in indirect contact with said gaseous mixture.

5. Apparatus of claim 1, wherein said first exchanger unit A comprises two exchanger stages positioned one above the other.

6. Apparatus of claim 5, wherein said first means includes means for introducing said first fraction of the refrigerant fluid at the highest temperature at a lower portion of said first exchanger A for upward circulation therein, and for introducing another fraction of the refrigerant at the next lowest temperature stage at a lower portion of the higher of said two exchanger stages for upward circulation therein.

- -UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN Patent No; 3,:7E47,36O I Dated Suizy 24, 193 73 Q Inventpfls) v TEAN CHARLES PERRET It is certified that errof 'appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, lines 66-67: replace "refrigerentf'lwith re f1 cigerant-- Column 4, line" 1: replace, "gaeeou s" with ---gas-- Column 4, line 38: after "two", replace "exchangers" wit h exchanger---' Signed and sealed this 26th day of November 1974;

Y (SEAL) Attest:

M CCOY GIBS QN JR. (1. MARSHALL DANN -Attest1ng Offlcer Cpmmissioner of Patents FORM 504050 "ch69, v I USCOMM-DC suave-p59 i [1.5. GOVERNMENT PRINTING OFFICE I969 O-lfiG-JSJ. 

2. Apparatus of claim 1, wherein said second exchanger unit B comprises two exchangers stages positioned one above the other.
 3. Apparatus of claim 2, wherein said third means includes means for introducing a fraction of the refrigerant fluid at the lowest temperature at an upper portion of said second exchanger unit B for downward circulation therein, and for introducing another fraction of the refrigerant liquid at the next preceeding temperature stage at an upper portion of the lower of said two exchanger stages for downward circulation therein.
 4. Apparatus of claim 1, wherein in each of said first and second exchanger units A and B, said gaseous mixture is confined in an exchanger conduit and said exchanger units A and B include means for passing the refrigerant fluid in indirect contact with said gaseous mixture.
 5. Apparatus of claim 1, wherein said first exchanger unit A comprises two exchanger stages positioned one above the other.
 6. Apparatus of claim 5, wherein said first means includes means for introducing said first fraction of the refrigerant fluid at the highest temperature at a lower portion of said first exchanger A for upward circulation therein, and for introducing another fraction of the refrigerant at the next lowest temperature stage at a lower portion of the higher of said two exchanger stages for upward circulation therein. 